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Nova Canaã, nestled in the state of Bahia, Brazil, at coordinates -14.7939, -40.1419, is a municipality deeply embedded within the semi-arid Sertão region. The town’s geography is characterised by a gently undulating terrain, typical of the Brazilian Northeast, with elevations ranging between 300 and 600 meters. This inland location, approximately 200km from the coast, means maritime influences are minimal, contributing to a more continental climate. The surrounding landscape is dominated by *caatinga* vegetation – a unique, drought-resistant scrubland – and scattered agricultural lands primarily dedicated to subsistence farming and, increasingly, large-scale soybean and corn cultivation. The urban character of Nova Canaã is that of a small, developing town, with a population of around 13,715, exhibiting a clear urban-rural gradient. Air quality is significantly influenced by this agricultural expansion, particularly during land preparation and harvest seasons when dust and biomass burning contribute to particulate matter. The lack of substantial industrial activity within the immediate vicinity means that local pollution sources are largely related to vehicle emissions, domestic fuel burning (wood and charcoal), and agricultural practices. The town’s position within a broad valley can also contribute to localised temperature inversions, trapping pollutants near the ground.

Nova Canaã experiences a pronounced wet and dry season, rather than traditional four seasons. The dry season, spanning roughly August to December, is the period of greatest concern for air quality. Reduced rainfall leads to increased dust resuspension from agricultural lands and unpaved roads, elevating particulate matter concentrations. This is often exacerbated by intentional burning for land clearing, a common practice during this time. Temperatures are high, and stable atmospheric conditions frequently lead to temperature inversions, trapping pollutants close to the ground. January to April marks the wet season, bringing significant improvements in air quality as rainfall effectively washes away particulate matter and suppresses dust. However, increased humidity can also promote the formation of mould spores, potentially impacting respiratory health. May to July represents a transitional period with moderate air quality. Sensitive individuals – children, the elderly, and those with pre-existing respiratory conditions – should be particularly cautious during the dry season (August-December), limiting strenuous outdoor activity and considering the use of respiratory protection. Monitoring wind patterns is crucial; winds from agricultural areas will carry higher pollutant loads. The months of February to April generally offer the most favourable conditions for outdoor activities.